Posts by mrl33h

Flask-Admin is a Flask extension that solves the boring problem of building an admin interface on top of an existing data model. With little effort, it lets you manage the data of your web application through a user-friendly interface. To make your data a little more interesting it is often useful to provide some images that can be integrated in slideshows, articles or even as an exchangeable logo of your application. While image uploads are indeed a very common task for web applications I found myself pondering frequently on how to realize a consistent integration in the Flask-Admin modelview system. Especially I wanted a solution that allowed me to upload images regardless of their filename and also handle duplicates graciously without breaking the association of my database entry to the referenced imagefile. So this article is about how to achieve consistent image file storage implemented in Flask-Admin by using the Flask-Uploads extension to automatically generate UUIDs as filenames and link them to a database entry.

One of the first IoT use cases that comes in ones mind ist measuring the temperature of your environment. An easy and cost-efficient way is to use an 1-Wire bus sensor like the DS18S20. You can get this sensor for around 2,15€ and it is really easy to implement in your µC as there are a bunch of libraries for the 1-Wire protocol. So the first thing to do is put the sensor in a bread board and connect it to your WiPy2 breakout board. The pin assignment is simple. Connect Pin1 of the sensor to GND, Pin2 to G10 and Pin3 to 3.3V. That' s it.

Lately I found a Beaglebone Black in my stock and had the idea to use it for some kind of fermentation control with a graphical user interface (GUI). For testing purposes I first wanted to run a small GUI on the Beaglebone via remote control (SSH). SSH has this great -X switch that enables X11 Forwarding. So I wanted to use this from my Mac to remote control the Qt GUI on my Beaglebone. Here is how I did it.

In recent months I really came to like Flask as a framework for creating websites and web applications. The usage of Jinja2 templates, HTML5 and Javascript to create good-looking and responsive user interfaces along with the Python language in the backend comes by naturally and on some point I asked myself why not to use Flask to create Desktop applications. The idea to use web technology for creating desktop applications is quite old and for other programming languages there exist some nice frameworks (e.g. Githubs Electron). However for Python there are not so many players around. So I decided to use the PyQt5 WebView widget. I have some experience with PyQt5 so this approach seemed the most natural to me. I wanted the application to become a stand alone executable. So I used cx_freeze here.

I wanted to be able to switch fast between different network configurations on my Windows development PC without using any kind of 3rd party software. So I had a quick look on Stackoverflow and found the beautiful wmi package. Windows Management Instrumentation (WMI) is Microsoft’s implementation of Web-Based Enterprise Management (WBEM), an industry initiative to provide a Common Information Model (CIM) for pretty much any information about a computer system. And the wmi package is a Python wrapper for it on top of pywin32.

Modal dialogs are quite common in GUI programming. They help to focus the users attention on the task at hand but still outline the context of the given or needed information by keeping the parent object visible in the background. As I have been doing a lot of classic GUI programming with PyQt I like to use modal dialogs and it feels natural for me to use them as well in Flask Web Applications. Bootstrap provides a great and simple way to create a modal dialog which is just what we want. However things get a bit more complicated when it comes to dealing with forms in modals. It took me a while to figure out a solution I am comfy with and I want to describe my solution in the following.

A while ago I wrote a post about how to serve a Flask application on a webserver. Today I want to write about how to achieve this by using a docker container. Using a container for deploying web applications has the main advantage of shipping an isolated environment in a Black Box to its destination. So you don' t depend on the server operating system or the configuration. You don' t have to worry about the right version of Python being installed and so on. Also the whole shipping mechanism via Docker Hub works great. So let' s get moving.

As a developer I endeavor to keep a consistent working environment on all of my computers. Meaning editing with VIM, version-controlling with GIT and using all the cool POSIX tools directly from the Terminal to do whatever. At home I use Mac OS X and for servers I use Debian. So working with the terminal is basically the same for both systems.

Unfortunately on Windows it is not as easy to setup a proper toolchain as it is not a Posix compliant operating system. So instead of a powerful shell like Bash with lots of helper tools you get the Commandline with almost nothing. Luckily there is Cygwin which brings some kind of Linux-flaire to Windows by providing Posix tools and a nice terminal called mintty. Still it is not the same as running on Linux but it is a step in the right direction. The main drawback using Cygwin is that you are still on Windows. Meaning you can't just clone a Github repository and compile it. When you do so there is always something missing. Also you keep running into trouble with Cygwins way of putting all drives in /cygdrive instead of using the native drive letters on Windows. So to get the real Linux feeling I decided to actually use real Linux ... in a virtual machine.

In my last post Checking out: Flask-Admin extension I gave a short introduction to the Flask-Admin extension. I also built a small example to show how easy it is to get a basic admin interface for your data.
But how does Flask-Admin work if we have more advanced requirements? For example what if we want to provide an image for each user? In this case we will have to expand our recent example by an Image model.

In my recent projects I often ran into the important but boring task of building admin interfaces on top of data models. It is important because using an admin interface it is the preferred way to edit, add and delete information. It is boring because it basically means you have to create two interfaces dealing with exactly the same data: the layout of the website that is shown to public and the interface for data administration. Flask-Admin is an addon for the Flask microframework that takes care of the boring part. With little effort, it lets you manage your web service’s data through a user-friendly interface.

Lately I wanted to test a new application before deployment and wanted to make it accessible via a subdirectory of my blog url. It doesn't sound like a great deal but I had some difficulties to accomplish it. To make my life easier in future and to help others facing the same challenge I wrote this Howto.

This is the final part of my tutorial on Flask Server Deployment. In the last section we configured our Gunicorn WSGI server and controlled it via Supervisor. In this section we will place our WSGI server behind a Proxy server.

This is Part 3 of my tutorial for Flask Webserver Deployment. In the last section we prepared our server for serving a Flask application. We created a small Flask test application and finally started up the Flask development server. In this part we will use a more production ready server called Gunicorn to run the application.

This is Part 2 of my tutorial for Flask Webserver Deployment. In the last section we acquired our own personal Linux server. Now we want to get connected to it and run our first Flask Test Application.

Hello World

Hello, my name is Stefan and I wrote this small blogging platform in Python using its great Flask microframework.
I was guided along the way by the very recommendable book "Flask Web Development"
from Miguel Grinberg. After some days of work this is my first post on this platform and it seems to work.

Why did I do it?

Actually I have been programming Python for a while now. It is a great programming language and for me it was just fun
to get to know more and more features of the language and available packages. I actually got into web-programming by
beer... , yes beer... I'm not only a coder but also a homebrewer (I will write about my brewing experiences in this blog
later on). To make my life as a homebrewer a bit easier I was working on a brewing controller, a Raspberry Pi controlling
my mashing and brewing temperatures. I first came in touch with Flask when I was looking for a way to build a nice-looking
GUI for the brewing controller. I immediately liked its simplicity and modularity. During the learning progress I came across
Miguel Grinbergs "Flask Mega Tutorial" in which
he points out the main features of Flask and some of its Addons by developing a microblogging platform. I liked it very much
so I decided to buy his book and create my own blog basing on it. So now we're here.

What will I write about?

I want to write about my coding experiences especially by extending the functionality of this blog. Also I want
to write about my brewing experiences and new beer creations. So I think there will be plenty to write about
in the time to come. To keep the orientation one of my next objectives will be to add Tags to the posts.